Incandescent lamp



Dec. 17, 1968 J,PALERMQ ETAL 3,416,851

INCANDESCENT LAMP Original Filed July 2. 1962 2 Sheets-Sheet 1 /1 1;141(5) QTL'IZIl FIG.5

JAMES J. PALERMO ROBERT P BONAZOLI ROBERT E SCOLEDGE EMERY G. AUDESSEINVENTOR ATTORNEY Dec. 17, 1968 J J, PALERMO ETAL. 3,416,851

INCANDBSCENT LAMP 2 Sheets-Sheet 2 Original Filed July 2, 1962 FIG.6

ROBERT F SCOLEDGE EMERY e AUDESSE INVENTORS 0 M R E m P S M A J ROBERTP. BONAZOLI FIG.9

ATTORNEY 3,416,851 INCANDESCENT LAMP James J. Palermo, Salem, N.H., andRobert P. Bonazoli, Hamilton, Robert F. Scoledge, Danvers, and Emery G.Audesse, Salem, Mass., assignors to Sylvania Electric Products Inc., acorporation of Delaware Original application July 2, 1962, Ser. No.206,881, now Patent No. 3,321,662, dated May 23, 1967. Divided and thisapplication Jan. 3, 1967, Set. N 0. 644,409

2 Claims. (Cl. 316-19) ABSTRACT OF THE DISCLOSURE A method of making anelectric lamp in which a tube of small diameter containing a filament isplaced inside and joined to a tube of larger diameter with a glass discslidable in the larger diameter tube. After exhaust the glass disc ismoved near the end of the lamp over the filament and spaced therefromand is sealed to the outer tube to form the completed device.

This is a division of application Serial No. 206,881, filed July 2,1962, now Patent No. 3,321,662 granted May 23, 1967.

This invention relates to incandescent lamps and particularly toincandescent lamps having a high power output in a small envelope, andto methods of making such lamps.

The invention is particularly useful in the so-called iodineincandescent lamp, in which a small amount of iodine vapor is present inthe envelope to prevent blackening of the latter during the useful lifeof the lamp, in accordance with the well-known tungsten-iodine cycle.Such iodine lamps are generally in the form of elongated sealed tubes,with a coiled filament along the axis of the tube, each end of the tubehaving a flat pressed seal through which a lead-in conductor extendsfrom the filament. Such tubular lamps, however, are diflicult to make inextremely small sizes, and have the disadvantage of requiring electricalcontact means at each end.

We have discovered that a very compact iodine lamp can be made bysupporting a coiled filament between two lead-in wires which passthrough a single pressed seal, at one end of a very small sealed bulbwhose opposite end is in the form of a thin flat glass disc,hermetically sealed thereto. The disc can be a glass lens, if desired.The resultant device will be capable of withstanding very high shockforces, thereby extending the field of application of the lamp. The wordglass is used in a broad sense, including quartz and other highlyrefractory glasses.

The external contacts, being entirely at the back of the lamp, do notinterfere with the light emitted forwardly.

The usual tubular iodine lamp has an exhaust tube midway between itsends. In the present lamp, that would correspond to an exhaust tube atthe forward or fiat disc end of the bulb, which would destroy theeffectiveness of the light emission through that end, and would preventthe use of a lens as the disc. This is especially true where the lamp issmall, and the exhaust tube would occupy a considerable proportion ofthe light-emitting area. The exhaust tube cannot extend from the pressseal at the contact end of the bulb, because of the small spaceavailable and the shape of the press seal.

We have discovered, however, that the device can be made without anyexhaust tube at all on the finished lamp, and have discovered a methodof so making the lamp.

Our method includes sealing the lamp mount into one end of an elongatedglass tube, the glass tube being sealed at its other end and having anexhaust tube intermediate the two ends and preferably in the middle ofthe tube. Be-

- United States Patent Patented Dec. 17, 1968 fore sealing the glasstube, a small, loosely-fitting glass disc or lens is slipped into thetube, and a shoulder is provided on the inside surface of the glass tubeabove the filament, so that the glass disc can be brought to restagainst the shoulder. The entire tube can then be exhausted through theexhaust tube and filled to the proper pressure with a suitable fillinggas such as argon or nitrogen and a small amount of iodine.

After the tube is evacuated and filled with the desired gases, smallpin-point flames are applied to the outside of the tube in register withthe outer circumference of the glass disc until the glass is heatedsufiiciently so that an hermetic seal will be effected between the tubeand disc. Once the seal is completed, the glass tube is cut off from theend of the lamp above the disc, and the edges firepolished if desired.

The result will be a lamp having no exhaust tube and whose forward orlight-emitting portion is a flat glass disc from which a small bulk-liketube extends rearwardly to merge into a press seal through which two ormore leadin conductors extend for contacts to an external circuit.

In some cases it may be desirable to have a filament at each end of thetube and two discs in the tube so that a small lamp can be made and cutolf from each end of the tube thereby increasing the efiiciency of themanufacture.

The glass disc inside the lamp can be replaced by a cupshaped glassmember, that is a short hollow cylinder closed at one end, with the openend of the cup facing the nearest end of the lamp. In that case theshoulder inside the tube can be omitted, and the open rim of the cupallowed to rest on the sealed end of the lamp, with the closed end ofthe cup enough away from the sealed end of the lamp so as not to touchthe filament. By this method, the sealing of a small-diameter tubeinside a larger-diameter tube is unnecessary, and a single-diameter tubecan be used. The cylindrical sides of the cup have an outside diameterslightly less than the inside diameter of the main portion of the tube,and after evacuation and gas-filling of the device are sealed to theouter lamp tube.

Other objects, advantages and features of the invention will be apparentfrom the following specification taken in connection with theaccompanying drawing in which:

FIGURE 1 is a view of two tubes of different diameters which are to besealed together;

FIGURE 2 is a view of the two tubes sealed together at their adjacentends, one tube being slightly inside the other;

FIGURE 3 shows the tube of smaller diameter shortened and an exhausttube sealed to the tube of larger diameter.

FIGURE 4 shows the same device with the smaller tube pressed to form aseal, through which lead-in wires extend to support a filament, the viewalso showing a small glass disc loosely fitting inside the tube;

FIGURE 5 shows a tube sealed at both ends with the filament in place atone end for sealing the disc to the tube;

FIGURE 6 shows the finished lamp after being cut from the tube of whichit was originally a part;

FIGURE 7 shows a cross-section of the same lamp through a middle planetransverse to that of FIGURE 6; and

FIGURE 8 shows a top view of the lamp.

FIGURE 9 is a view of a lamp ready for processing, using a glass cupinstead of a disc.

In making a lamp according to the invention a hollow glass tube 1 andanother glass tube 2, whose outer diameter is slightly smaller than theinside diameter of tube 1, are lined up with each other. As shown inFIG- URE 2, the tube of smaller diameter 2 is pushed a short distanceinto an adjacent end of tube 1 and the two tubes then sealed together,the smaller tube forming the shoulder 3 inside the end of the largertube 1. Up to this point the tube 2 has been kept rather long forconvenience in handling and the excess is now out ofi leaving only asmall length of tube 2 extending from FIGURE 1. An exhaust tube 4 issealed into the side of the tube 1 and considerably away from theshoulder 3.

The open end 5 of the smaller tube 2 is now pressed together to form afiat press through which the molybdenum ribbons 6, 7 are sealed, one endof each ribbon being joined to the lead-in wire 8, 9 which extends outof the glass seal at its external end. The other end of each ribbon 6,7, is joined to a support wire 10, 11 which extends therefrom into thetube to carry a coiled filament 12. The filament is generally acoiled-coil as shown more clearly in FIGURE 6, and the primary orsmaller coil of the coiled-coil may extend straight downwardly over thesupport wires 10 and 11 and be fixed thereto.

A thin glass disc or lens 13 is slipped onto the open end into thetube 1. This disc should have a diameter somewhat smaller than theinside diameter of tube 1, so that it may slip easily down the tube, asshown by the arrow in FIGURE 4, when the tube is placed vertically as inFIGURE 5. For example, if tube 1 is of 0.300 inch inside diameter, thedisc 13 can be of 0.284 inch outside diameter, or may even have adiameter somewhat close to the inside diameter of the outer tube 1. Theend 14 of tube 1 is sealed off, for example to form a press seal 15, asshown in FIGURE 5, at the top of the tube, or in some other convenientmanner. The device is exhausted and filled in the usual way with asuitable filling gas such as nitrogen or argon and a small amount ofiodine. The disc being loose-fitting, will permit evacuation and fillingof the portion 16 of the tube below the disc, when in the position shownin FIG. 5. However, the evacuation and gas-filling will be greatlyfacilitated if the disc 13 is in the position shown in FIG. 4, or is ina position with its flat sides parallel to the longitudinal axis of tube1 instead of transverse to it, during the exhausting and filling. Flamesof the narrowed, pin point type to confine their heat to a small portionof the glass are applied to opposite sides of the glass tube 1 and inhorizontal relationship with the disc 13 and the glass sufficiently toeffect a permanent hermetic seal between the disc 13 and the tube 1, thedisc 13 resting on the shoulder 4.

After the disc 13 is sealed to the tube 1, as in FIG. 6, the tube 1 iscut off flush with the top of the disc, and the remaining cut edgesground or fire-polished, if desired, resulting in the finished lamp ofFIGS. 6, 7 and 8.

In these figures, the disc 13 is the top portion of the lamp as shown inFIG. 6 and all that remains of outer tube 1 is the outer portion of thecylindrical wall of the lamp as shown. The inner portion of the wall iswhat was once the smaller-diameter tube 2, and is so marked in thefigures. The filament 12 can be of a coiled coil type, and if the tubes1 and 2 were of about 0.375 inch and 0.300 inch outside diameterrespectively, and each about 0.035 inch thick, with the disc 13 havingabout the same thickness, and the formed bulb of the lamp being aboutA-inch from the beginning of the press seal to the top of the disc 13,this distance being denoted by A in FIG. 7. In such a small lamp, madeof quartz, a power input of 100 watts was used, the filament being acoiledcoil tungsten filament designed for that wattage. The diiferencein size between this kind of 100-watt lamp and the usual 100-watt lampsold for home use, and generally having a bulb about 2% inches indiameter, is quite apparent. Moreover, the construction of our resultantbulb is much more resistant to shock than is the usual incandescentbulb.

A modified method of making a lamp is illustrated in 4 FIG. 9. In this,the tube 1 is sealed ofi directly at one end by a press seal carryingthe filament 12, rather than through the intermediary of a smallerdiameter tube 2. The shoulder which the latter tube would provide is notused in FIG. 9, because the disc 13 is now in the form of a cup 20, thatis of a hollow cylinder 21 with the disc 13 sealed to and closing oneend. At its open end the cylinder 21 will rest on the press seal,thereby spacing the disc 13 above the filament. The cup 20 is placed inthe tube 1 while the end 22 of the bulb is open, before sealing it as atseal 23.

The cup 20 makes a slightly loose fit in the tube 1 to permit evacuationand gas-filling of the end of the tube around the filament 12. After theevacuation and gas-filling, the cylinder 21 is sealed to the tube 1, andthen the latter cut off flush with the side of the disc 13 flush withthe filament, as before. The resultant lamp is shown in FIG. 10.

Although a particular lamp has been described, the examples are givenmerely as illustrative, and various modifications can be made by aperson skilled in the art without departing from the spirit and scope ofthe invention. For example, a reflecting coating of metal or of theso-called dichroic types, can be used on the outside of the bulb portion25, or even on the inside, if very refractory materials are used.Platinum and palladium would be good metal coatings for hightemperatures; dichroic materials are shown in a copending applicationSerial No. 24,101, filed April 21, 1960, by R. F. Scoledge et al.

The word light as used in the appended claims includes all forms ofradiation emitted from an incandescent filament or electric discharge,such as infra-red or ultraviolet in addition to visible light, and alight-transmitting piece is intended to mean a piece transmitting anydesired light in any or all of the ultraviolet visible and infra-redregions.

Although the invention has been described with respect to 'anincandescent lamp, it can also be used in an electric discharge lamp, inwhich the lead-in wires would carry electrodes through which a dischargecould be passed.

What we claim is:

1. The process of making an electric lamp, said process comprising:placing adjacent ends of two tubes together, one tube being smaller thanthe other and fitted into the adjacent end of the other; sealing the twotubes together at said ends, so that one forms a shoulder near the endof the other; sealing otf the smaller tube a short distance from the endand outside the other tube, a pair of lead-in wires passing through saidseal and carrying a wire filament between them; placing a glass discinside larger tube; sealing ofi the other end of said tube; evacuatingand gas-filling said tube; allowing the disc to drop onto the shoulder;and sealing the disc to the tube while resting on said shoulder.

2. The process of making an electric lamp, comprising: sealing one endof a glass tube with lead-in wires passing through the seal; placing acup-shaped glass piece in said tube with the open end of the cup facingthe filament; exhausting and gas filling said tube while keeping the cupaway from the filament; allowing the cup to drop toward the filamentuntil the open end of the cup rests on the restricted portion of thetube near the seal; sealing said cup to said tube by heat appliedexternally to the tube; cutting otf the portion of the tube on theclosed side of the cup.

References Cited UNITED STATES PATENTS RICHARD H, EANES, JR., PrimaryExaminer

